A wavelength division multiplex (Wavelength Division Multiplex, WDM) optical network is capable of performing multiplexing, transmission, amplification, route selection, and restoration on a signal in an optical domain, which has become a study hotspot in a field of optical communications. According to that whether a node of a WDM optical network performs electronic processing on an optical signal, optical networks may be divided into two types: a transparent (Transparent) network and an opaque (Opaque) network. For a transparent optical network, a signal is in a form of an optical signal all the way in a process of being transmitted from a source node to a destination node, and regeneration, exchange and wavelength conversion of the signal are completed in an optical domain. Since the node is incapable of regenerating an electric signal, the transparent optical network is essentially an analogue transport network. Since each network unit does not perform electric processing on an optical signal, information impairment cannot be eliminated in a transmission process. Therefore, transparency of the WDM may cause performance degradation of a transmitted optical signal, which may become severer as a network scale expands and a transmission distance increases. Performance factors that may affect performance of an optical signal include: optical fiber dispersion, optical fiber nonlinearity, crosstalk (especially inter-band crosstalk), and erbium doped fiber amplifier (Erbium Doped Fiber Amplifier, EDFA) noise integration.
In a WDM Network, after a group of connection requests are given, routes need to be established and wavelengths need to be assigned for the connection requests, and this is referred to as a problem of routing and wavelength assignment (RWA, Routing and wavelength assignment). Apart from the RWA, when establishing an optical path connection in a WDM transparent optical network, the mentioned performance factors also need to be considered to ensure that an established optical path can normally bear transmission of a signal. The performance factors are called physical impairment. Two solutions that are adopted to implement transmission control based on the physical impairment include a centralized solution and a distributed solution. In the former solution, an independent centralized control unit is responsible for routing and wavelength assignment, and performance assessment and parameter calculation. In the latter solution, more flexible performance control is implemented by expanding a control plane protocol.
In a distributed control mode, a transport network expands the control plane protocol to implement distributed transmission control, which includes a solution of a distributed signaling manner.
In the distributed signaling manner, the transport network expands signaling to implement online dynamic estimation of optical signal quality and physical parameter adjustment in a procedure of establishing an optical path. In this manner, a current routing protocol does not need to be altered, and each node only needs to store a local information database. By introducing an object that includes a network physical transmission parameter into a multi-protocol label switching protocol, when a path establishment request is received, a source node performs source routing calculation, and then signaling collects physical parameters of each node, an associated link, and an adjustable device from the source node to a destination node. An optical path assessment module is introduced at a destination end and performs assessment on performance of an optical path with reference to the physical parameters. If calculated transmission impairment does not exceed a tolerable range, a node establishes a connection and at the same time returns a response message to the source node. In a returning process, transmission equipment is reset according to an optical path assessment result. The distributed signaling manner does not require global flooding of physical parameter information of any link, but merely collects physical parameter information of each node and link through which the signaling passes in a path establishment message, and a path assessment module of the destination node performs judgment and calculation. The main advantages of the distributed signaling manner lie in that a network resource may be saved and a problem of communication synchronization may be avoided.
In an existing distributed signaling method, performance of an optical path is assessed at a destination end. Specific assessment manners are mainly divided into two kinds: The first is that a head node does not designate a wavelength during calculation of source routing, signaling carries physical impairment parameters of multiple wavelengths (wavelength set) along the way, and one of the wavelengths is selected at a tail node as an assigned wavelength of the path establishment request according to the physical impairment parameters of the multiple wavelengths; and the second is that a head node designates a wavelength during calculation of source routing, signaling carries a physical impairment parameter of the wavelength along the way; and whether the physical impairment parameter of the wavelength satisfies a requirement is verified at a tail node, and if the physical impairment parameter of the wavelength does not satisfy the requirement, the head node is instructed to re-select a path or a wavelength.
The existing solutions put forward that impairment assessment is performed at a tail node. This processing manner causes that the tail node receives too many physical impairment parameters of wavelengths, so that the amount of redundant information is quite large, and at the same time, a path establishment delay is increased.